Platform adapter: rename System_Essentials, add Plugin/unraid/adapter.sh, wire call sites

- Rename unRAID_Essentials/ → System_Essentials/ (git detects as rename)
- Add Plugin/unraid/adapter.sh: 13 platform_*() functions providing OS-agnostic API
  for storage health, service management, mover, user scripts, notifications,
  disk temps, and platform command validation
- Update load_config.sh: detect PLATFORM (unraid/truenas/unknown), export SCRIPTS_DIR,
  auto-source Plugin/$PLATFORM/adapter.sh after common.sh
- Wire all call sites: replace direct rc.d, pgrep/pkill, var.ini, dynamix.cfg,
  disks.ini, and validate_unraid_cmd calls with platform_*() functions across
  watchdogs, orchestrators, and System_Essentials scripts
- Update all documentation: rename refs, update webgui escalation logic,
  add platform adapter section to Plugin README, update main README with
  portability vision and corrected self-healing stack description

README-User_Script_Plug-in.md

@@ -72,7 +72,7 @@ Rsync              — manual per-profile sync triggers
 Docker_Essentials  — container management tools (manual use)
 Media              — library maintenance tools (manual use)
 Transcodes         — ramdisk and transcode tools (manual use)
-unRAID_Essentials  — server management tools (manual use)
+System_Essentials  — server management tools (manual use)
 Partnership        — two-server relationship tools (manual use)
 Tools              — repair, recovery, and one-time utilities
 Git                — script deployment
@@ -1190,7 +1190,7 @@ flip count, session split ramdisk vs SSD).
 ### ── webgui_watchdog ───────────────────────────────────────────────────────────
 
 ```
-Category:   unRAID_Essentials
+Category:   System_Essentials
 Name:       webgui_watchdog
 Schedule:   */10 * * * *  (every 10 minutes)
 Background: YES
@@ -1221,7 +1221,7 @@ A notification fires on any restart so you know what recovered and when.
 ### ── clear_logs ───────────────────────────────────────────────────────────────
 
 ```
-Category:   unRAID_Essentials
+Category:   System_Essentials
 Name:       clear_logs
 Schedule:   0 5 * * 0    (Sunday 5am — before Sunday maintenance window)
 Background: YES
@@ -1229,7 +1229,7 @@ Background: YES
 
 ```bash
 #!/bin/bash
-/boot/config/plugins/varaverk/unRAID_Essentials/clear_logs.sh
+/boot/config/plugins/varaverk/System_Essentials/clear_logs.sh
 ```
 
 **What it does:**
@@ -1248,7 +1248,7 @@ Active containers like Emby and SABnzbd grow fastest. Truncation not rotation
 ### ── stability_watchdog_status ──────────────────────────────────────────────────
 
 ```
-Category:   unRAID_Essentials
+Category:   System_Essentials
 Name:       stability_watchdog_status
 Schedule:   None — run manually
 Background: NO
@@ -1269,7 +1269,7 @@ watchdog-triggered reboots. All 18 per-host toggle states.
 ### ── mover_stop ───────────────────────────────────────────────────────────────
 
 ```
-Category:   unRAID_Essentials
+Category:   System_Essentials
 Name:       mover_stop
 Schedule:   None — run manually (before array operations needing mover stopped)
 Background: NO
@@ -1277,7 +1277,7 @@ Background: NO
 
 ```bash
 #!/bin/bash
-/boot/config/plugins/varaverk/unRAID_Essentials/mover_stop.sh
+/boot/config/plugins/varaverk/System_Essentials/mover_stop.sh
 ```
 
 **What it does:**
@@ -1290,7 +1290,7 @@ files). Waits + verifies. SIGKILL if still running (warns that partial files are
 ### ── rsync_stop ────────────────────────────────────────────────────────────────
 
 ```
-Category:   unRAID_Essentials
+Category:   System_Essentials
 Name:       rsync_stop
 Schedule:   None — run manually (when rsync needs stopping)
 Background: NO
@@ -1298,7 +1298,7 @@ Background: NO
 
 ```bash
 #!/bin/bash
-/boot/config/plugins/varaverk/unRAID_Essentials/rsync_stop.sh --status
+/boot/config/plugins/varaverk/System_Essentials/rsync_stop.sh --status
 ```
 
 **What it does:**
@@ -1312,7 +1312,7 @@ exits cleanly. No orphaned lock files. Containers recover via docker_watchdog.sh
 ### ── user_scripts_stop ────────────────────────────────────────────────────────
 
 ```
-Category:   unRAID_Essentials
+Category:   System_Essentials
 Name:       user_scripts_stop
 Schedule:   None — run manually (before reboots, or when a script hangs)
 Background: NO
@@ -1320,7 +1320,7 @@ Background: NO
 
 ```bash
 #!/bin/bash
-/boot/config/plugins/varaverk/unRAID_Essentials/user_scripts_stop.sh --status
+/boot/config/plugins/varaverk/System_Essentials/user_scripts_stop.sh --status
 ```
 
 **What it does:**
@@ -1334,7 +1334,7 @@ by server_reboot.sh before reboot.
 ### ── server_reboot ────────────────────────────────────────────────────────────
 
 ```
-Category:   unRAID_Essentials
+Category:   System_Essentials
 Name:       server_reboot
 Schedule:   None — run manually (planned maintenance reboots)
 Background: YES — sequence takes 1-2 minutes
@@ -1342,7 +1342,7 @@ Background: YES — sequence takes 1-2 minutes
 
 ```bash
 #!/bin/bash
-/boot/config/plugins/varaverk/unRAID_Essentials/server_reboot.sh --dry-run
+/boot/config/plugins/varaverk/System_Essentials/server_reboot.sh --dry-run
 ```
 
 **What it does:**
@@ -1587,7 +1587,7 @@ Background: NO
 
 ```bash
 #!/bin/bash
-/boot/config/plugins/varaverk/unRAID_Essentials/git_pull_execute.sh
+/boot/config/plugins/varaverk/System_Essentials/git_pull_execute.sh
 ```
 
 **What it does:**